How to Best Insulate a Vaulted Ceiling?

Compared to the common flat ceilings, vaulted ceilings can be a bit more difficult to insulate. Even though they look nice, and make the space seem bigger and brighter, they allow the warm air in your home to rise, and escape no matter how well your heating works.

Good insulation for vaulted ceilings is therefore super-important. You will maintain a comfortable temperature in your home while saving money on energy bills. To insulate a vaulted ceiling, you’ll probably need scaffolding or walk boards to reach its rising angle, so before you start, make sure you prepare all the necessary tools and materials for that project.

In this article, we’ll summarize the step-by-step process and different types of insulation materials you can consider.

How Hard Is It to Insulate a Vaulted Ceiling?

Vaulted ceilings can be harder to insulate than regular flat ones because gravity works against you. Flat ceilings under an attic are much easier to approach and can be insulated with literaríy any type of insulation material.

When it comes to vaulted ceilings, you’d probably need to think twice, as some insulation materials will probably be better and easier to use than others in that case.

What Are the Best Options for Insulating a Vaulted Ceiling?

In theory, you can use any insulation material to insulate your ceilings, but for the tall vaulted ceilings, you would want to find the most practical options. As the narrow space between the sloped roof and ceiling often isn’t enough for thicker insulation batts, you would probably need to consider getting thinner insulation material, with a higher R-value (an insulation factor), like cellulose or spray foam, for example.

Thinner and lighter insulation batts may be a bit more pricey like blown cellulose, or alternatively, a spray foam which is made to fit surfaces that are difficult to reach. Let’s take a look at a few insulation materials and compare their effectiveness.

Batt Insulation

As mentioned above, if you go for batt insulation, you’d probably need to choose a thinner, and a bit more expensive, specialized batts for your vaulted ceilings, and even then, you would need to count on the risk of air leaking through and around them if not fitted perfectly.

Batt insulation like fiberglass or mineral wool counts as an affordable insulation material, however, its quality can decrease over time. Unfortunately, the batts you install are going to shift and settle with time and release more and more air to come through.

Vaulted ceilings aren’t the easiest to insulate because of their shape and height, and you can expect that they will allow more unprotected tiny paths for the air to come through. Be especially aware of the electrical wiring and any other obstacles on your ceiling because those areas may be extra difficult to insulate.


Cellulose can be a bit better than batt insulation because of its thickness and higher R-value. If you choose blown-in cellulose and apply it properly, you can insulate even more difficult spaces and cover all the gaps around the electrical cables or ceiling beams.

If you choose to insulate your vaulted ceiling with cellulose be aware that cellulose can also expand to its natural thickness. Because of this, you may need some professional help guiding this process and making sure that packing will resist settling.

Even though cellulose isn’t permeable to air, some building regulations may require you to install ventilation between the roof and the insulation, and in cases like those, where cellulose doesn’t fit perfectly, some air leak will be possible. In those situations, fiberglass insulation may be more effective on vaulted ceilings than cellulose.

Spray foam

Spray foam has a higher insulation factor than both fiberglass and cellulose. It is made of a few compounds and is applied by water pressure. The material expands after application to completely seal all the cavities in the walls and ceilings.

Spray foam can be applied during the construction of the house, or later injected into the walls when renovating. If this material is your choice, you’d need a professional to help you complete the project, as spray foam can be messy to install and requires special equipment and experience with handling.

Prodex Total

A closed-cell foam insulation material that comes in light rolls, and products of different sizes and thicknesses can be another great option for insulating a vaulted ceiling. This light material has an exceptionally high R-value and combines the advantages of all other insulation materials:

  • Has a high R-value
  • Blocks radiant heat transfer from the outside
  • Prevents air leaks
  • Stops condensation or moisture
  • Doesn’t support mold
  • Blocks rodents and insects
  • Provides sound insulation

Prodex Total is made of closed-cell foam and reflective foil that covers it from both sides. Prodex is easy to transport, easy to measure and cut, as well as to install. In many cases, it can be used for DIY insulation projects, on walls, ceilings, and floors, so it can also be a great choice for insulating your vaulted ceiling.

How to Insulate a Vaulted Ceiling — Step by Step?

1. Choose the insulation

There are various types of vaulted ceilings, as well as different types of insulation. The very first step is to determine what insulation method and material will suit your home best, and what would be the most practical option for installation.

You can choose from mineral wool, fiberglass, cellulose, or rigid foam insulations. The factors to consider when starting this process are the R-value of the insulation material, the moisture resistance, and finally, your budget.

2. Prepare the space

Before you start, clear out your workspace and make sure there is no debris or any obstacles on your way. If you are renovating an old house, and there is already existing insulation, decide if and how you want to remove it before installing the new one.

3. Measure the ceiling properly

No matter if you’re planning to use batts or blown-in insulation, you need to measure the surface you want to insulate and measure it right. Use a measuring tape and measure the space between the rafters on the ceiling, and then multiply that by the length of the rafters. That’s how you’ll know how much insulation material you need.

4. Fit the insulation

Use the measures you have to cut the insulation properly or determine how much of the material you need. Make sure that the pieces of insulation will fit snugly onto the ceiling, and don’t be afraid to cut any large piece in two if that will make it easier for you to apply it. Be careful when pressing the insulation material into place, as it shouldn’t be compressed.

5. Safety

Don’t forget the safety measures before you or anyone who’s helping starts the insulation work. Get protective gear like masks, goggles, and gloves to protect your health from dust and tiny pieces of insulation material, especially if you are working with fiberglass or spray foam.

6. Vaulted ceiling insulation installation

Start at one end of the ceiling and place the insulation between the rafters. If your choice was batt insulation, gently press it into the surface and make sure it fills the entire cavity. If the insulation has a vapor retarder (paper or foil) place it facing down and staple the rims until it fits snugly.

If you are using rigid foam, repeat a similar process but attach it to the ceiling using adhesive tape or fasteners.

7. Make sure the gaps are sealed

After the installation, do a thorough checkup of the ceiling making sure all the gaps are sealed. If you find any that aren’t, use the caulk or insulation foam to seal them.

Electrical fixtures and wiring in the vaulted ceiling can bring additional complications. While insulating it, make sure you don’t cover them with the insulation but install baffles that are specially made for this purpose and your safety. On the other hand, make sure there are no gaps around the wires and fixtures that would allow a lot of air to leak in.

8. Ventilation

Proper ventilation is important and often required by the local building regulations. It will prevent moisture in your home by allowing airflow between the roof and your ceiling. Find out how to install ventilation chutes and baffles before you start your insulation project.

9. Inspection

Before you completely finish the insulation of your vaulted ceiling, make sure to check once again for gaps and air leaks, as well as for proper ventilation and the space around the electrical fixtures. If needed, make additional adjustments rather than risking air or moisture leakage in the future.

Insulating a vaulted ceiling isn’t an easy project to handle on your own, so don’t hesitate to hire or consult professionals and get to know more about the insulation installation process.

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